Evidence of superparamagnetic nanoparticles from Mössbauer spectroscopy study of Co0.5Ni0.5-xSrxFe2O4 nanoparticles

Abstract

Co0.5Ni0.5-xSrxFe2O4 powders with x values of 0.1, 0.2, 0.3, 0.4 and 0.5 were quickly produced using the Solution Combustion Synthesis (S.C.S.) method. The effects of strontium (Sr) concentrations on the structure, microstructure, and magnetic properties were investigated using a variety of characterization methods. The SC technique produced single-phase spinel ferrites with a space group of Fd-3m (JCPDS data: 01-074-5694) directly and did not require any additional heat treatment throughout the manufacturing process. The lattice parameter increased due to the addition of the Sr ions, but the redistribution of the various cations resulted in a drop in the fraction of the Fe3+ cations found in the (A) sites. The average crystallite size reduced from 23 to 19 nm. Scanning Electron Microscopy (S.E.M.) displays well-shaped spherical grains in the nanoscale region, but larger grains with agglomeration were discovered with Sr doping of spinel ferrite nanoparticles. Room temperature Mössbauer spectra have a structure typical for superparamagnetic nanoparticles. To determine the distributions of iron ions at the A- and B- sites, the low-temperature measurements of Mössbauer spectra were performed at 15K, where the effect of relaxation on the structure of Mössbauer spectra is negotiable, the concentration of iron ions in A- and B-site were determined. It has been established that the substitution of Nickel ions for Strontium ions leads to the growth of FeA3+/FeB3+ ratio from 0.75 to 0.89. In this study, we show the effect of Sr doping on the structure, morphology and magnetic properties Co–Ni ferrite nanoparticles, which are suitable for a wide variety of applications because of their adaptability.